Credit Suisse admitted yesterday that a “small group of Swiss-based private bankers” at the bank had helped private clients from the United States to evade taxes, but said that it had been done without the knowledge of senior management.

Brady Dougan, the chief executive, told a US Senate hearing that the Swiss bank had turned over a new leaf since before the financial crisis, when Swiss banking secrecy laws were abused by American taxpayers seeking to hide money.

“While that employee misconduct violated our policies, and was unknown to our executive management, we accept responsibility for and deeply regret these